Exhaust valves for internal combustion engines



Oct. 8, 1963 A. G. HELLSTROM Filed Oct. 16, 1961 EXHAUST VALVES FOR INTERNAL COMBUSTION ENGINES //lllfl/I II I I,

flll//////////// United States Patent In internal combustion engines of the type having exhaust valves arranged in the cylinder head, it can be difficult to provide for an efiective sealing between the valve stem and its guide. As known the gas has an overpressure in relation to the atmosphere and this fact in connection with the movement of the valve stem prevents a good sealing of mechanical nature.

It has already been proposed arrangements for removing impurities gathered between the valve stem and the guide. Usually these arrangements comprise an annular recess in the guide which is connected to the inlet valve conduit by a passage. This has essentially been made in order to prevent external lubricating oil from entering along the stem and as there will be a vacuum in the inlet conduit during other times than the exhaust periods, such a system will be of no value with respect to impurities accompanying the exhaust gases. The present invention is based upon Bernoullis law, which states that ed downwards in the exhaust conduit, the gas velocity will on the other hand he proportionally high in the constriction around the guide and for that reason the pressure p H will here be low.

The invention relates to an arrangement for valves, the guide of which is provided with an annular recess and is characterized by that the valve guide in the above mentioned manner is extended downwards in the exhaust conduit and that said recess by one or more passages is connected to the exhaust conduit in the constriction formed around the guide. The recess will by this be connected to the exhaust conduit at a place, where the velocity is high. The pressure in the annular recess will by means of this be low, so that a leakage along the valve stem is limited.

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In the accompanying drawing the invention is shown by Way of example as applied to a large internal combustion engine. The cylinder head 1 is only indicated by dash-dotted lines. A special valve housing 2 is fitted into the head and a valve guide 3 is arranged in said housing. The'guide member extends a distance downwards in the portion 4 which forms the beginning of the exhaust conduit. The exhaust valve 5 with its stem and disc ootains an efiective guiding as the valve guide extends in the conduit portion.

When the gases reach the lower part of the valve guide, the velocity is reduced, and the gases are forced under increase-d pressure into the clearance 7 between the stem and the lower part of the guide. A distance from the end part 6 an annular recess 8 is located, adapted for the expansion of the gas. The recess 8 is by one or more passages 9 connected to the conduit portion 4. The passages are obliquely directed along with the flow of gas in the exhaustconduit, whereby a certain ejector action is obtained. Possible solid particles which have reached the clearance will thereby be sucked out through the passages. The cross section of the passages ought to be greater than the area of the clearance between the valve stem and the lower part of the guide. Owing to the low pressure in the recess 8 there is only a small tendency of leakage upwards along the stem. The number of passages 9 and their positions in relation to the gas current may be determined by the conditions of the gas flow and the shape of the exhaust conduit.

What I claim is:

In an internal combustion engine cylinder head, an exhaust conduit having a lower essentially straight portion terminating in a valve seat and an upper curved portion terminating in a lateral exit portion, and an overhead poppet valve for opening and closing said conduit, said valve having a stem, a guide for the stern of said valve extending .freely into said essentially straight portion of the exhaust conduit to a point below the lower boundary of said lateral exit portion and forming a constriction in said essentially straight portion, an internal annular recess in said guide located at some distance from the end thereof closest to the valve seat but wholly within the exhaust conduit, said internal recess communieating with the constricted part of the exhaust conduit solely by means of the valve stem clearance area and one or more narrow passages which are obliquely directed in the direction of the exit end of said conduit.

References Qited in the file of this patent UNITED STATES PATENTS 1,552,547 Disch Sept. 8, 1925 1,712,539 Willgoos May 14, 1929 

